1. Field of the Invention
The present invention relates to a coil spring compressor which is used in the assembly of subassemblies of automotive front or rear suspension systems, in particular, MacPherson type suspension systems.
2. Description of the Prior Art
Certain types of automotive suspension system such as of the MacPherson type comprise a suspension subassembly. The subassembly includes a strut formed by a lower tube. The strut includes a built-in shock absorber. A part of a piston of the shock absorber projects upward from the strut in a telescoping fashion. A coil spring is mounted in a compressed state around the strut between a lower spring seat integral with the strut and an upper spring seat fastened to the upper end of the piston of the shock absorber. Such a suspension subassembly is assembled separately and then mounted as a unit in a vehicle body.
During the assembly of a MacPherson type suspension subassembly, the coil spring is passed from above around the stanchion with its lower end abutting against the lower spring seat. The coil spring is then compressed by a suitable power tool to bring the upper end of the coil spring below the upper end of the piston of the shock absorber, so that the piston upper end protrudes beyond the coil spring upper end. The upper spring seat is then fastened to a threaded part of the upper end of the shock absorber piston by a nut. As a result, the coil spring is retained between the upper and lower spring seats in a compressed state.
In the copending patent application Ser. No. 453,839 filed Dec. 28, 1982, and assigned to the assignee of the present invention, there is disclosed a coil spring compressor suitably used for compressing a coil spring during the assembly of MacPherson type suspension subassemblies. This coil spring compressor comprises a base, a movable head plate positioned above the base for translational movement thereto, and means for driving the head plate toward and away from the base. The head plate is provided with a pair of spaced guide bars connected thereto and suspended therefrom. A clamp carriage is mounted on the guide bars for vertical sliding movement through a predetermined distance. The clamp carriage is provided with a frontal opening having a sufficient size to receive therethrough without interference a coil spring to be compressed. The clamp carriage is provided with four clamping arms, each of which is pivoted at an end to the carriage and is provided at the other end with a clamping hook projecting toward and engageable with any selected turn of the coil spring. The four clamping arms are grouped into two pairs, one of which is arranged along one side of the frontal opening of the carriage and the other along the opposite side. The front and rear clamping arms in each pair are interlocked with each other so that when the front arm in each pair is rotated toward and away from the coil spring, the rear arm swings conjointly with the front arm toward and away from the coil spring. The front clamping arm in each pair is provided with an operating handle. In use, the operator first slides the clamp carriage upward and downward along the guide bars and adjusts the vertical position of the carriage so that the clamping hooks are leveled between the desired successive turns of the coil spring, normally between the first and second turns. Then, the operator closes the handle together to insert the clamping hooks between the selected turns of the coil spring and turns on the drive means to lower the head plate. As the head plate travels downward, the clamping hooks are urged againt the second turn of the spring and compress the same to the desired degree.
In the coil spring compressor of the type described, however, the operator has to actuate both operating handles at one time in order to bring the four clamping hooks into engagement with the coil spring. In addition, the speeds of closing movement for each operating handle must be the same in order to position the coil spring concentrically with the MacPherson strut. If one of the handles is moved faster than the other, the pair of clamping hooks associated with that handle will first engage the coil spring, causing it to displace toward the other pair of clamping hooks until it abuts against the latter. This will result in the coil spring being off center with respect to the strut.